1. Field of the Invention
The present invention relates to a data processing apparatus, a data processing method and an image forming apparatus which can be used as a MFP (Multi Function Product) with multiple functions such as a copying function, a printer function, a scanner function and a facsimile function.
2. Description of Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
To realize the multiple functions, a MFP as mentioned above is equipped with a plurality of input portions such as a receiving portion for receiving print data sent from an external apparatus, such as a personal computer (hereinafter referred to as “PC”), via a network and/or an original reading portion for reading an original.
Further equipped are a printer portion for printing the image data read by the original reading portion or the print data from the external apparatus, a working memory for storing a data-to-be-outputted inputted from each input portions and a file memory for storing the once-inputted data for second and subsequent sets of outputting operations.
In order to minimize the storage capacity of the data to be stored in the file memory, in general, a plurality of compressing/expanding devices for compressing or expanding data are connected in parallel. The data spread on the working memory is transferred to the compressing/expanding devices to be compressed, and the compressed data is stored in the file memory.
In such a MFP, in cases where image data of an original read by the original reading portion is inputted, the inputted image data is spread on the working memory and the spread data is transferred to the printing portion for printing. Simultaneously, the data is transferred to the compressing/expanding devices to be compressed and then stored in the file memory. In cases where a second set of printing operation is executed, the compressed data stored in the file memory is expanded by the compressing/expanding devices and transferred to the working memory again. Then, the data is transferred to the print portion for executing the printing operation.
As mentioned above, however, in cases where image data from the original reading portion is transferred to the compressing/expanding devices to be compressed while being transferred to the printer portion, it is necessary to synchronize the image reading portion and the printer portion. As a result, it is difficult to drive the original reading portion at a rate faster than the operating speed of the printer portion, which deteriorates the entire processing ability of the apparatus.
It may be considered not to synchronize the original reading portion with the printer portion such that the image data from the original reading portion is transferred to the compressing/expanding devices to be compressed therein without being transferred to the printer portion and thereafter the compressed image data is expanded and then the expanded image data is transferred to the printer portion.
In this case, however, in cases where the image data is data including a large amount of information such as color image data, it takes a time to compress and expand the image data. Accordingly, the initiation of the printing operation will be delayed. As a result, there is a problem in processing performance as an entire apparatus.
U.S. Pat. No. 6,381,031 discloses a technique in which the assignment of the compression/expansion operation to be allotted to the compressing/expanding devices connected in parallel is changed depending on the quantity of the data-to-be-outputted. For example, the U.S. Patent discloses that, in cases where the code data is read out from the file memory while being thinned out or only the code data of even-numbered pages is read out, since the quantity of data to be stored in the file memory is greater than that of the image data to be read out, the number of the compressing/expanding devices for executing the compression operation increases and that for executing the expansion operation decreases. Furthermore, the U.S. Patent discloses that, in the case of a sort copy, all of the compressing/expanding devices are used to compress the data of the first original, half of them are used to compress and expand the data of the second and subsequent originals, and all of them are used to expand the compressed data after the completion of storing the data.
According to the technique disclosed in the aforementioned U.S. Patent, although it discloses an efficient operation of the compressing/expanding devices, it fails to disclose that the image reading portion is operated at a rate faster than the operation speed of the printer portion. Thus, it was not enough to solve the aforementioned problems.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.